Method for the mask-etching of a piercing element

ABSTRACT

A method is disclosed for the mask-etching of a piercing element having an elongate shaft, a distally protruding tip, a proximal holding part, and a laterally open collecting channel that collects bodily fluid and extends along the shaft as far as the area of the tip, wherein a side of a double-sided etching mask is applied respectively to the two sides of a substrate and, under the action of an etching agent, the piercing element is formed as a part made by chemical blanking, wherein a channel side of the etching mask is provided with a channel etching slit for unilateral etching of the collecting channel.

This application is a divisional of U.S. patent application Ser. No.14/221,990 filed Mar. 21, 2014, now U.S. Pat. No. 9,522,566, which is acontinuation of international Application No. PCT/EP2012/068426 filedSep. 19, 2012, which claims priority to European Patent Application No.11182455.3, filed Sep. 23, 2011, which are hereby incorporated byreference.

An embodiment of the invention relates to a method for the mask-etchingof a piercing element which has an elongate shaft, a distally protrudingtip, a proximal holding part, and a laterally open collecting channelthat collects bodily fluid and extends along the shaft as far as thearea of the tip, in which method a side of a double-sided etching maskis applied respectively to the two sides of a substrate and, under theaction of an etching agent, the piercing element is formed as a partmade by chemical blanking, wherein a channel side of the etching mask isprovided with a channel etching slit for unilateral etching of thecollecting channel. An embodiment of the invention further relates to acorrespondingly produced piercing element.

An etching method is disclosed in WO 2006/066744 A1 for producingdisposable piercing elements for the recovery of small amounts ofsamples, such as those that are withdrawn in situ from a skin incisionas capillary blood for blood glucose determinations. The latterdocument, however, proposes an etching mask layout for a capillarychannel that is open at the front and closed at the proximal end,wherein the piercing tip protrudes distally from the rear face directedaway from the channel. A problem also lies in avoiding interferencecontours in the piercing process caused by the channel walls jutting upat the front end.

Proceeding from this, the object of the invention is to further optimizethe etching methods known in the prior art, and the piercing elementsgenerated by said methods, and to improve the collecting of samples andthe transfer of samples in integrated diagnostic systems.

This object is achieved by the combination of features indicated in theindependent claims. Advantageous embodiments and developments of theinvention are set forth in the dependent claims.

The invention is based on the concept of optimizing the end of thecollecting channel for the collection and transfer of samples. It isthus proposed, according to an embodiment of the invention, that aproximal and/or distal end portion of the channel etching slit isdesigned to taper toward the end of the slit.

It is thus possible to ensure, on the one hand, that, during the etchingprocess, the channel cross section in the front distal tip area tapersor at least remains constant and no bone-shaped widening occurs at thechannel end as a result of flow processes of the etching agent. Even ifsuch a “bone formation” were to be classed at first as non-critical forthe uptake of liquid in the tip area, this could nevertheless lead toetching-through in the area of the tip, on account of the reducedmaterial thickness. Accordingly, the collecting channel would not beable to be guided far forward, and the increased distance between tipand channel end would necessarily lead to a deeper depth of incisionand, therefore, to an increased sensation of pain. In order to reducethe depth of incision and to ensure optimal collection of samples orblood, it is therefore essential that the capillary channel alreadycomes into contact with blood or tissue fluid during the incision underthe skin. Such a configuration of an etched part is achieved using anetching mask in which the channel etching slit is guided as far as thedistal tip area and thereby tapers.

On the other hand, the tapering of the etching slit at the proximal endhas the effect that the etched collecting channel terminates at the rearend with a constant or even decreasing capillary diameter, such that thecapillary transport is not interrupted too early, as would beunavoidable in the case of capillary widening by standard etchingtechniques.

In an advantageous embodiment, the end portion of the channel etchingslit is tapered linearly, such that the etched collecting channelextends in the direction of the taper with a constant or continuouslydecreasing cross-sectional area.

In order to support a capillary-active transfer of samples, it isadvantageous if the channel etching slit is positioned in a proximalregion of the etching mask, such that the etched collecting channelopens out at the front end on the holding part.

A further improvement in terms of sample handling in an integrated testconfiguration can be achieved by virtue of the fact that the etchingmask is provided with a flange-forming area, which adjoins the channeletching slit in the proximal direction, and that, by undercutting theflange-forming area, a preferably straight flange edge forming the mouthof the collecting channel is generated, in particular for flanging atest element onto the holding part.

In order to give the mouth a planar limit, it is advantageous if theflange-forming area has a mask bridge extending, transversely withrespect to the channel etching slit, across the proximal slit endthereof.

In a further improvement in terms of a defined configuration of theholding part, it is proposed that the etching mask is provided with asacrificial continuation, which is arranged at a proximal distancedownstream of the channel etching slit and which serves to screen anetching agent effect in the mouth area of the collecting channel.

For the radial screening of a half space behind a mask edge, it isadvantageous if the sacrificial continuation protruding freely on themask edge is defined by an arc shape, in particular a circular arcshape, in an edge area directed away from the proximal slit end of thechannel etching slit. The dimensions of the sacrificial continuation areto be adapted to the undercutting width of the etching agent, such thatthe sacrificial continuation is completely etched off to its proximalbase. In principle, other geometries of the sacrificial continuation arealso conceivable, for example rectangular or triangular, in order tomake available a screening surface that has a suitable edge distance anda certain expanse for protecting the mouth area of the collectingchannel from the etching medium.

In another embodiment, the etching mask is provided, on both sides ofthe substrate, with a tip-forming area in order to form a tip contour,wherein the channel-side tip-forming area is arranged distally in frontof the tip-forming area lying on the opposite side. In this way,sufficient substrate material is also available in the area of the tipfor a collecting channel that is routed as far forward as possible,while the cutting action is not impeded by interference contours on theopposite side.

In order to further reduce any interference contours, it is advantageousif the etching mask, on its opposite side directed away from the channeletching slit, has an auxiliary opening, in particular for avoidingundercut edges in the area of the tip.

Advantageously, the auxiliary opening is arranged in a tip-forming areaof the etching mask at a lateral distance from a mask edge. In thisconnection, it is particularly expedient if the auxiliary opening hastwo auxiliary opening limbs extending toward each other in a V shape inthe distal direction, and if the auxiliary opening has a distalauxiliary opening continuation, which extends in the distal directionbeyond the auxiliary opening limbs and which is preferably designed as aslit or series of holes.

To avoid barbs or undesired humps, the end of the auxiliary openingcontinuation, seen in the proximal direction, should lie behind thedistal end of the tip to be formed.

It is accordingly expedient if the auxiliary opening is Y-shaped,wherein the connection point of the opening limbs extending toward eachother is arranged at a distal distance from the tip contour to beformed.

For samples to be already taken up in the skin, it is particularlyadvantageous if the channel etching slit is extended so far into adistal tip-forming area of the etching mask that the collecting channelterminates at a distance of 50 to 1000 μm, optionally 150 to 400 μm,before the distal end of the tip.

In another advantageous embodiment, the tapered end portion of thechannel etching slit is reduced in width, along a length in the range ofbetween 100 and 300 μm, by 0.4 to 0.6 times its initial width, toward ablunt end edge.

A further aspect of an embodiment of the invention concerns a piercingelement with an elongate shaft, a distally protruding tip, a proximalholding part, and a laterally open collecting channel that collectsbodily fluid and extends along the shaft as far as the area of the tip,wherein the collecting channel, at least at one end portion, extendswith a continuously decreasing cross-sectional area and is formed by amask-etching method as claimed.

The invention is explained in more detail below on the basis of anillustrative embodiment depicted schematically in the drawing, in which:

FIG. 1 shows a plan view of a distal, channel-side mask portion of anetching mask for producing a piercing element provided with a collectingchannel;

FIG. 2 shows an area of the piercing element generated with the maskportion according to FIG. 1;

FIG. 3 shows a distal, rear-side mask portion in a view corresponding toFIG. 1;

FIG. 4 shows an area of the piercing element generated with the maskportion according to FIG. 3;

FIG. 5 shows a plan view of a proximal, channel-side mask portion;

FIG. 6 shows an area of the piercing element generated with the maskportion according to FIG. 5;

FIGS. 7 and 8 show a cross section through the etching mask and thepiercing element along the section lines 7-7 and 8-8 in FIG. 9; and

FIG. 9 shows a perspective view of the piercing element formed as a partmade by chemical blanking, in conjunction with a test element flanged onat the proximal end.

An etching mask 10 shown in the drawing is applied as a double-sidedlayout onto the two sides of a thin stainless steel substrate in orderto form a piercing element 14 as a part made by chemical blanking which,according to FIG. 9, has an elongate shaft 16, a distally protruding tip18, a proximal holding part 20, and a collecting channel 22 thatcollects bodily fluid (blood, tissue fluid) from a skin incision andextends along the shaft 16 as far as the area of the tip 18 and ishalf-open or groove-shaped along its length. The piercing element 14 canbe combined, as an integrated diagnostic consumable, with a test element24, in order to transfer the sample fluid received in the capillarycollecting channel 22 to a reagent layer 26 for determining an analyte(e.g. glucose). The test element 24 can be fixedly integrated on thepiercing element 14 right from the outset, or it can be connected to thepiercing element 14 only later for the transfer of the sample.

The etching mask 10 can be structured on the substrate 12 byphotolithography, i.e. by exposure and washing out from photoresist, ina manner known per se. Through the recesses in the thus generatedetching mask 36, the substrate 12 is then subjected to an etching agent,wherein the covered or masked areas are etched free according to thebasic shape. It must be ensured that the material removal takes placenot only depthwise but also by back-etching or undercutting of edgecontours of the etching mask 10. As a result of external parametersinfluencing the substrate or as a result of material properties of thesubstrate, the etching process can also take place anisotropically, i.e.the lateral undercutting rate or width is then greater or lesser thenthe depth etching rate.

The channel side 28 of the etching mask 10 in a distal portion shown inFIG. 1 has a shaft-forming area 30 for the shaft 16, and a tip-formingarea 32 for formation of the tip 18. Starting from a constriction 34,the tip-forming area 32 is adjoined in the distal direction by awidening screening area 36, which prevents frontal etching-off of thetip 18, such that a particularly sharp tip contour is etched free onlyby lateral undercutting of the tip-forming area 32.

Further details of such screening for contouring of the tip are set outin WO 2006/066744, to which reference is made in this connection. In thelatter, however, the distally protruding tip area is arranged on thesubstrate side (designated there as rear side) directed away from thecapillary channel, whereas the capillary channel open at the front islaterally limited only behind the tip.

In the mask layout according to the invention, a channel etching slit 38is provided on the channel side 28 for unilateral (groove-shaped)etching of a collecting channel 22, which terminates in the area of thetip 18 and is closed at the front. For this purpose, a distal endportion 40 of the channel etching slit 38 is designed to taper towardthe distal slit end 42 lying in the tip-forming area 32.

FIG. 2 shows an enlarged detail of the etching mask 10 according to FIG.1 in broken lines, in conjunction with the etched-free distal portion ofthe piercing element 14. It will be seen from this that the linear taperof the end portion 40 of the channel etching slit 38 is chosen such thatthe etched collecting channel 22 extends with continuously decreasingwidth and depth into the area of the tip 18.

The substrate thickness is expediently in the range of 100 to 300 μm.The width of the channel etching slit 38 in the central part can beabout 100 to 150 μm, while the tapered end portion 40, along a length of100 to 300 μm corresponding approximately to the substrate thickness, isreduced by approximately half its initial width toward a blunt end edgeforming the slit end 42. It can thereby be achieved that the collectingchannel 22 terminates at a short distance in the range of 150 to 400 pmbefore the distal end 44 of the tip 18.

FIG. 3 shows a distal portion of the etching mask 10 on the oppositeside 46 directed away from the channel side 28. The two mask sides 28,46 are positioned relative to each other such that the positioning orindexing holes 48, 48′ lie concentrically with respect to one another.Also on the opposite side 46, the etching mask 10 has a shaft-formingarea 30′ for the shaft 16, and a tip-forming area 32′ for the formationof a tip contour. A screening area 36′ is arranged distally in front ofthe tip-forming area 32′ in order to avoid bluntness at the front. Inaddition, a Y-shaped auxiliary opening 50 is provided for avoidingundercut edges and humps in the area of the tip contour on the channelopposite side 46, as is explained in more detail below.

The tip-forming area 32′ on the opposite side 46 is set back in theproximal direction in relation to the channel-side tip-forming area 32,such that the tip 18, seen in the longitudinal direction, has a convexrounding starting from the distal end 44.

As will be seen from FIG. 4, a tip contour tapering in a wedge shape viaedges 54 to a vertex 52 is generated on the piercing element 14 by thetip-forming area 32′ on the opposite side 46. The vertex 52 expedientlylies, by more than the substrate thickness, in the proximal directionbehind the channel-side distal end 44. The opening limbs of theauxiliary opening 50, which spread out approximately parallel to theedges 54, ensure that the edges 54 are rounded convexly in cross sectionby additionally penetrating etching agent and do not form a hollow.Correspondingly, the connection point 56 of the opening limbs 50′tapering toward each other is arranged distally in front of the vertex52, such that no undercut barb impeding the incision forms in thelongitudinal direction either. If the connection point 56 were arrangedfurther forward, it would no longer be possible to achieve such aneffect. By contrast, if it were moved further to the rear, a kind oftransverse channel with a hump lying in front of it would be obtained.In order to avoid a contour of this kind that disrupts the needleincision, the auxiliary opening 50, starting from the connection point56, has a distal base limb or auxiliary opening slit 50″, whichpreferably extends with uniform width in the distal direction. Theauxiliary opening slit 50″ terminates at a proximal distance in relationto the channel-side distal end 44 of the tip 18 to be formed. In thisway, the greater width of the channel-side tip-forming area 32 is takeninto account.

FIG. 5 shows a proximal (rear) region 58 of the etching mask 10 on thechannel side 28, which region 58 is provided for generating the holdingpart 20. The channel etching slit 38 can run out there in an end portion60 tapering in the proximal direction. In principle, this rear endportion 60 can be dimensioned according to the front, distal end portion40. The channel etching slit 38 can be positioned in the mask region 58in such a way that the etched collecting channel 22 opens out at thefront on the holding part 20, in order to permit a linear capillarytransport of the sample fluid to the test element 24.

For docking of the test element 24, the mouth area of the collectingchannel 22 should as far as possible have no widening of its crosssection, as this could stop the capillary transport of liquid. Likewise,the test element 24 should lie flat thereon without an air gap. Toachieve this, the etching mask 10 is provided with a flange-forming area62, which adjoins the channel etching slit 38 in the proximal direction.The flange-forming area 62 has a mask bridge 64 which extendstransversely with respect to the channel etching slit 38, across theproximal slit end thereof, which mask bridge 64, with uniformundercutting, leads in the distal direction to a rectilinear edgecontour.

However, in addition to the distal undercut, the etching agent alsoflows via the channel etching slit 38 in the proximal direction andwould lead to a corresponding widening of the etching at the mouth. Inorder to compensate for this effect, the etching mask 10 is providedwith a sacrificial continuation 66, which is arranged downstream at aproximal distance from the channel etching slit 38 and which prevents adistal etching agent effect in the mouth area of the collecting channel22.

To achieve this, the sacrificial continuation 66 protruding freely onthe mask bridge 64 is arc-shaped in a proximal edge area, wherein theradius is adapted to the undercutting width such that the sacrificialcontinuation 66 is completely etched off.

FIG. 6 shows that, by means of the mask layout described above, astraight flange edge 68 is generated in the holding part 20 and leads tooptimized sample transfer to the flanged-on test element 24. Thesacrificial continuation 66 not only ensures a rectilinear boundary ofthe mouth 70 of the collecting channel 22, but also prevents anadditional widening of the etching of the channel end portion. It willbe appreciated that the proximal region of the etching mask 10 for theopposite side has no channel etching slit and, accordingly, has nosacrificial continuation. In other respects, however, it corresponds tothe proximal region 58 on the channel side.

As is also clear from FIGS. 7 and 8, the structural contours andtopography of the piercing element 14 are defined by the different masklayout on the two sides of the substrate 12. In addition to the surfaceetching of the fine collecting channel 22 on one side, the depth etchingvia the mask openings 70, 72 also achieves a separation of the chemicalblanking part in the substrate, wherein a corresponding mask repetitionpermits the production of large batch numbers, if appropriate from rollto roll.

1. A piercing element comprising an elongate shaft, a distallyprotruding tip, a proximal holding part, and a laterally open collectingchannel configured for collecting bodily fluid and extending along theelongate shaft as far as the area of the tip, wherein the collectingchannel, at least at one of its end portions, extends with acontinuously decreasing cross-sectional area and is formed by amask-etching method in which a double-sided etching mask is applied totwo sides of a substrate and, under the action of an etching agent, thepiercing element is formed as a part made by chemical blanking, whereina channel side of the double-sided etching mask is provided with achannel etching slit for unilateral etching of the collecting channel,wherein the channel etching slit has a proximal end portion and a distalend portion located opposite the proximal end portion, wherein theproximal and/or distal end portion of the channel etching slit isconfigured to taper toward the end of the channel etching slit.
 2. Thepiercing element of claim 1, wherein the double-sided etching mask isprovided with a flange-forming area, which adjoins the channel etchingslit in a proximal direction, and the flange-forming area is undercut toform a flange edge forming a mouth of the collecting channel.
 3. Thepiercing element of claim 2, wherein the flange edge is configured forflanging a test element onto the proximal holding part.
 4. The piercingelement of claim 3, wherein the flange-forming area comprises a maskbridge extending transversely with respect to the channel etching slitacross a proximal slit end thereof.
 5. The piercing element of claim 1,wherein the proximal and/or distal end portion of the channel etchingslit tapers linearly, such that the etched collecting channel extends inthe direction of the taper with a constant or continuously decreasingcross-sectional area.
 6. The piercing element of claim 1, wherein thechannel etching slit in a proximal region of the double-sided etchingmask is positioned such that the etched collecting channel opens out atthe front end of the proximal holding part.
 7. The piercing element ofclaim 1, wherein the double-sided etching mask comprises a sacrificialcontinuation, which is arranged at the proximal end portion downstreamof the channel etching slit and which is used to screen an etching agenteffect in a mouth area of the collecting channel.
 8. The piercingelement of claim 7, wherein the sacrificial continuation protrudesfreely on a mask edge and is defined by an arc shape in an edge areadirected away from a proximal slit end of the channel etching slit. 9.The piercing element of claim 7, wherein the dimensions of thesacrificial continuation are adapted to an undercutting width of thesubstrate in response to the etching agent, such that the sacrificialcontinuation is completely etched off to its proximal base.
 10. Thepiercing element of claim 1, wherein the double-sided etching maskcomprises, on both sides of the substrate, a tip-forming area in orderto form a tip contour, wherein the tip-forming area on the channel-sideis arranged distally in front of the tip-forming area lying on the sideopposite the channel-side.
 11. The piercing element of claim 1, whereinthe double-sided etching mask, on its opposite side directed away fromthe channel etching slit, comprises an auxiliary opening which serves toavoid making of undercut edges in the area of the distally protrudingtip.
 12. The piercing element of claim 11, wherein the auxiliary openingis arranged in a tip-forming area of the double-sided etching mask at alateral distance from a mask edge.
 13. The piercing element of claim 11,wherein the auxiliary opening comprises two auxiliary opening limbsextending toward each other in a V shape in a distal direction.
 14. Thepiercing element of claim 11, wherein the auxiliary opening has a distalauxiliary opening continuation which extends in a distal direction. 15.The piercing element of claim 14, wherein a proximal end of theauxiliary opening continuation, as viewed in the proximal direction, isarranged behind a distal end of the distally protruding tip to beformed.
 16. The piercing element of claim 14, wherein the auxiliaryopening is designed as a slit or series of holes.
 17. The piercingelement of claim 11, wherein the auxiliary opening is Y-shaped andcomprises opening limbs extending toward each other, and wherein aconnection point of the opening limbs is arranged distally from a tipcontour to be formed on a side opposite the channel-side.
 18. Thepiercing element of claim 1, wherein the channel etching slit isextended so far into a distal tip-forming area of the etching mask thatthe collecting channel terminates at a distance of 150 to 400 μm beforethe distal end of the distally protruding tip.
 19. The piercing elementof claim 1, wherein the proximal and/or distal tapered end portion ofthe channel etching slit is reduced in width, by 0.4 to 0.6 times itsinitial width, toward a blunt end edge.
 20. The piercing element ofclaim 1, wherein the channel etching slit, at its proximal and/or distalend portion, is tapered toward the slit end along a length in the rangeof between 100 and 300 μm.